JP2012504056A - Method for forming a container such as a bottle from a preform made of a thermoplastic polymer - Google Patents

Abstract

A method for forming a container having a long body having a neck such as a bottle (2) from a preform (1) formed of a thermoplastic polymer, wherein the bottle (2) has special dimensional parameters. Having a method. The method comprises stretch blow molding a thin wall (10) preform (1) having an aspect ratio u = 1 / e with an average thickness (e) of the wall (10) of less than 2 mm and greater than 45. Where l is the length of the thin wall preform (1).
[Selection] Figure 1

Description

  The present invention relates to a preform (preform) formed from a thermoplastic polymer, preferably a thermoplastic polyester, most preferably a polyester comprising at least 92.5% of single elements derived from terephthalic acid and ethylene glycol. The present invention relates to a method for forming a container having an elongated main body having a neck such as a bottle. Another subject of the present invention is a bottle or similar container obtainable by said method and a thin-wall preform adapted to form such a bottle or similar container obtainable by said method. .

  At present, bottles made of polyester material are known which have water, juice, carbonated soft drinks and the like inside. Among the polyesters in which the number of simple substances derived from terephthalic acid and ethylene glycol occupies at least 92.5%, polyethylene terephthalate (PET), which is widely used for producing liquid bottles, is known. Its main attributes are transparency, low weight, better gas barrier than polypropylene, and the possibility of producing various shapes depending on the outer shape of the container such as the bottle it is desired to obtain.

It is known to produce bottles by injection molding starting with a preform formed from a polyester such as PET in the shape of a test tube, the open end of the preform already has the dimensions and final shape of the neck. Have. The preform is reheated, stretched in the longitudinal direction by a stretching shaft or rod, and blow-molded in a mold by introducing pressurized air into the preform. The bottle thus formed by omnidirectional deformation of the preform is then subjected to aseptic filling in a sterile environment, which is intended to sterilize its inner and outer surfaces before its standard filling. , Dried using hot air at a temperature of 70 ° C. Aseptic processing consists in using, for example, hydrogen peroxide (H ₂ O ₂ ) and sterile water at a temperature of 140 ° C.

  However, the mechanical properties of PET are greatly degraded when it is exposed to high temperatures that cause deformation of the material due to its shape memory, which tends to return to its initial shape. Thus, it has been found that during the step of sterilizing bottles that are exposed to hot gas for a specific processing time, the bottles shrink and that certain weight bottles tend to shrink more than lower weight bottles.

  Thus, to limit bottle shrinkage, standard solutions vary the amount of PET material, and thus the weight of the preform and bottle, its dimensions, length and / or perimeter, and its wall thickness. It is to increase by.

  Nevertheless, these dimensional changes may cause some of the cost of manufacturing the container due to the reduced amount of PET material due to preforms having shorter and / or smaller perimeters and / or smaller wall thicknesses. It is an obstacle to the reduction of

  One solution to reduce manufacturing costs while maintaining or increasing the weight of the preform by changing its dimensional parameters such as length or perimeter is to compensate for the wall thickness of the preform. It is possible to reduce the thickness.

  However, in the field of injection molding of parts such as preforms formed from PET material, in order to ensure easy and effective filling of the mold, in particular it has a value greater than 2.0 mm. A certain threshold must not be exceeded with respect to the wall thickness of the preform that must be and with respect to the ratio of the length of the preform to the wall thickness of the preform that must be less than 45 It is essential.

  If these thresholds are expected to be exceeded, one solution is to increase the cavity temperature or injection rate and pressure during the preform injection molding process. However, changing the cavity temperature has the negative effect of causing crystallization of the PET material and reducing the transparency of the container. Also, the increase in injection speed and pressure causes damage to the structure made of PET material due to the high shear rate.

  Furthermore, polyesters such as PET used in the manufacture of bottles for food applications can be used with the properties used, in particular with the inherent viscosity (IV) of the materials used, i.e. the length of the polymer chains used. It has an effect known as a “barrier effect” against various gases (steam, oxygen, carbon dioxide, etc.) that increase with it. Thus, materials with good gas impermeability are generally viscous (IV from 0.72 dl / g to 0.83 dl / g).

Intrinsic viscosity (IV) means the viscosity at zero concentration of a solution of a polymer, and this value is determined by the following formula: IV = −10 ⁻¹ VI ² + 0.94VI + 0.0122 ) Calculated by determining dl / g and the index consists of a mixture of orthodichlorobenzene and phenol (50/50 by weight) according to the standard ISO 1628/5 dated 15/06/1986 Measured on 0.5 g polymer solution in which the polymer was dissolved at 25 ° C. in 100 ml solvent.

  The object of the present invention is to limit the shrinkage effect of the bottle, and thus a single unit derived from a thermoplastic polymer, preferably a thermoplastic polyester, most preferably terephthalic acid and ethylene glycol, obtained during the high temperature aseptic filling stage. By overcoming these drawbacks by providing a method of forming a container having an elongated body with a neck, such as a bottle, from a preform formed of polyester comprising at least 92.5% is there.

  According to studies conducted by the applicant, the cause of this bottle shrinkage is not the amount of material, and thus the resulting weight, but the preform and final bottle dimensional parameter values that result in a very high draw ratio. It became clear that. Three of the stretch ratios are considered important: the stretch ratio “a” of the circumference, the stretch ratio “b” of the length, and the stretch ratio “c” of the surface.

  In particular, for two preforms having different dimensions and approximately the same weight, the stretch ratios a, b, c are higher for preforms having small dimensions and are thus obtained from preforms having small dimensions. It has been found that the shrinkage of the bottle is greater than the shrinkage of the bottle obtained using the other preform with the larger dimensions.

  In other words, these results show that the weight of the preform can be maintained or reduced and the dimensional parameters changed, contrary to the current preconception that the amount (weight) of PET material would cause the bottle to shrink. This shows that even lower draw ratios can be obtained, thus limiting the shrinkage of the bottle.

  In view of these results, the present invention provides a preform formed from a thermoplastic polymer that can limit the shrinkage of the final bottle, particularly when the final bottle is exposed to high temperatures during its sterilization step. A method of forming a container having an elongated body with a neck, such as a bottle, is provided.

From a preform formed from a thermoplastic polymer, preferably a thermoplastic polyester, most preferably a polyester comprising at least 92.5% of a single unit derived from terephthalic acid and ethylene glycol, and provided with a neck such as a bottle A method according to the invention for forming a container having an elongated body, wherein the open end of the preform has the shape and dimensions of the neck of the final bottle, and the bottle has the following dimensional parameters: ,
Pb: the maximum outer peripheral length of the final bottle;
L (1/2): The method with the side half length of the final bottle, i.e. the length measured from its bottom to the neck along its shape of the final bottle is
On the one hand, the following dimensional parameters:
Pp is the average circumference of the neutral fiber of the thin wall preform measured from the bottom to the neck of the preform, the length of the neutral fiber in the cross section of the preform,
l (1/2): the half length of the side of the thin wall preform, ie the length of the thin wall preform measured from its bottom to the neck along its shape;
l: the length of the preform and
e: the average thickness of the wall of the thin-wall preform from the bottom surface to the neck,
u: aspect ratio, u = l / e, on the other hand, with respect to the final bottle, stretch ratios a, b, c (a = Pb / Pp, b = L (1/2) / l (1/2 ), Essentially comprising stretching and blow-molding a thin-walled preform with c = a × b) wherein the dimensional parameter is the following threshold condition:
e <2 mm and u> 45
Set to meet
In the stretching and blow molding steps, the stretching ratio is as follows:
a <5; b <4 and c <16
It is performed so that it may satisfy | fill.

  The invention will be better understood from the following description, given by way of non-limiting example and described with reference to the accompanying schematic drawings, in connection with one preferred embodiment.

1 shows a schematic cross-sectional view of a bottle formed from a thin-wall preform according to the present invention. Figure 2 shows a schematic cross-sectional view of a thin wall preform according to the present invention in which the wall thickness varies along its body. Fig. 3 shows a cross-sectional view according to A-A of Fig. 2a showing the neutral fiber of the cross-section of the preform.

FIG. 1 comprises an elongate body with a neck 20 and comprises at least 92.5% of a single body derived from a thermoplastic polymer, preferably a thermoplastic polyester, most preferably terephthalic acid and ethylene glycol. Shown is a final bottle 2 manufactured from a preform 1 made of polyester, the open end of the preform 1 has the shape and dimensions of the neck 20 of the final bottle 2, the final bottle 2 being Dimensional parameters, i.e.
Pb: the maximum outer peripheral length of the final bottle 2 and L (1/2): the side half length of the final bottle 2, that is, the length measured from the bottom surface 20 ′ to the neck 20 along the shape of the final bottle 2. Have

The method according to the invention essentially consists, on the one hand, of the following dimensional parameters:
Pp: the average circumference of the neutral fiber 3 (FIG. 2b) of the preform 1 measured from the bottom surface 11 to the neck 20 (FIG. 2a) of the preform 1, in the cross section of the preform 1 of the thin wall 10 The length of the neutral fiber 3,
l (1/2): the length of the side half of the preform 1, that is, the length of the preform 1 of the thin wall 10 measured from its bottom surface 11 to the neck 20 along its shape;
l: the length of the preform 1 of the thin wall 10;
e: the average thickness from the bottom surface 11 to the neck 20 of the wall 10 of the preform 1 of the thin wall 10;
u: aspect ratio, u = l / e, on the other hand, with respect to the final bottle 2, stretch ratios a, b, c (a = Pb / Pp, b = L (1/2) / l (1 / 2) stretching the thin wall 10 preform 1 with c = a × b) and blow molding the dimension parameter is the following threshold condition:
e <2 mm and u> 45
Set to meet
In the stretching and blow molding steps, the stretching ratio is as follows:
a <5; b <4 and c <16
It is done to satisfy.

  The thin-wall 10 preform 1 according to the present invention is a thermoplastic polymer, preferably a thermoplastic polyester, most preferably PET or the like, wherein the number of simple substances derived from terephthalic acid and ethylene glycol accounts for at least 92.5% Preferably, it is formed from a polyester.

The preform 1 of the thin wall 10 according to the present invention is:
Injecting a hot plastic melt of polymer into a mold that is not completely closed;
A step of closing the mold,
Pressing the melt into its final shape;
Extracting the preform 1 of the thin wall 10 from the mold;
May be manufactured by a process consisting essentially of:

In a variant, the preform 1 of the thin wall 10 is
Placing the molding polymer in an open mold;
A step of closing the mold,
Pressing the melt into its final shape;
Extracting the preform 1 of the thin wall 10 from the mold;
May be manufactured by a process consisting of:

  Various compression molding processes for forming plastic products are known. For this, reference is made, for example, to EP 1 480 803 or WO 01/32390.

  The thin-wall 10 preform 1 according to the invention is injected by means of a plurality of injection gates with very high pressure or melt temperature (pressure> 150 bar and temperature> 280 ° C.) by gas or fluid injection techniques. May be. Alternatively, the preform 1 of the thin wall 10 can be extruded as a tube and finished into a preform 1 having one open end and a neck 20 or the preform 1 of the thin wall 10 is formed from two parts. Thus, the neck 20 can be connected to the main body of the preform 1 by, for example, friction welding.

In another variation, the preform 1 of the thin wall 10 may be manufactured by using an intrinsic viscosity (IV) polymer. Intrinsic viscosity (IV) means the viscosity at zero concentration of a solution of a polymer, and this value is determined by the following formula: IV = −10 ⁻¹ VI ² + 0.94VI + 0.0122 ) And the index is determined in 100 ml of solvent comprising orthodichlorobenzene and phenol (50/50 by weight) mixed according to standard ISO 1628/5 of 15 June 1986. Is measured on 0.5 g polymer solution in which the polymer was dissolved at 25 ° C. Advantageously, the intrinsic viscosity (IV) is 0.7 dl / g or less. Preferably, a polymer having an IV of 0.45 dl / g to 0.65 dl / g, most preferably 0.5 dl / g to 0.6 dl / g is selected.

  Advantageously, the polyester is derived from terephthalic acid, its ester, or a mixture of it and an aliphatic diol, such as ethylene glycol, 1,3-propanediol, or 1,4-butanediol.

  Preferred monomers are terephthalic acid and ethylene glycol which give polyethylene terephthalate, better known by the abbreviation PET as described above.

  As used herein, the term PET refers to homopolymers derived only from monomers of terephthalic acid or their esters, such as dimethyl terephthalate, and ethylene glycol, and co-polymers having a number of repeating ethylene terephthalate units of at least 92.5%. Polymers are also covered.

  According to a preferred feature of the present invention, the polyester obtains crystallization to very small crystals while avoiding spherical crystallization, and also has a transparent article with acceptable mechanical properties whose walls are not blurred. At least one crystallization inhibitor for slowing or slowing the crystallization of the polyester, especially during cooling of molded or poured articles such as preforms.

  These crystallization inhibitors are bifunctional compounds such as dibasic acids and / or diols which are added to the mixture of monomers before or during polymerization of the polyester and are well known by those skilled in the art (European Patent No. No. 041035 and EP 1417247).

  This is because a decrease in intrinsic viscosity occurs with macromolecules and even smaller sized macromolecules, and when the cavity is filled for the purpose of forming the preform 1 of the thin wall 10, the pressure over the entire length of the cavity. This is because the drop is small, so that for the same injection pressure, it is possible to obtain a high aspect ratio u, in particular an aspect ratio u greater than the value 45 imposed for shaping the current preform.

  These processes and the use of low IV polymers as defined above produce a thin wall 10 preform 1 with a thickness e less than 2 mm and an aspect ratio u greater than 45, and the melt is thin wall In order to prevent flow through the cavity, the filling of the molding cavity can be ensured easily and effectively. They also make it possible to obtain a thin-walled 10 preform 1 in which the thin-wall 10 does not tear during the stretching stage of the thin-walled preform 1.

  Beyond the thresholds for thickness e and aspect ratio u, the dimensions of the preform can be increased, thus reducing the stretch ratio and using such a thin-wall preform with the method of the present invention. Can limit the shrinkage effect of the final bottle obtained during the disinfection stage. On the other hand, by reducing the wall thickness e of the preform, it is possible to keep the same amount of material in the preform despite the increase in its dimensions, or compared to the current preform of the same dimension Can be saved.

  For example, formed from a preform X having a weight p = 14.5 g, a length l = 78.0 mm, a neutral fiber average circumference Pp = 52.0 mm, and a side half length l (1/2) = 64.2 mm For a 50cl final bottle with a maximum perimeter length Pb = 196.5 mm and side half length L (1/2) = 253.7 mm, the stretch ratio is a = 3.87, b = 3.90, and c = 15.1 and approximately the same weight p = 14.2 g as the preform X, but larger dimensions, i.e. l = 86.0 mm, Pp = 56.5 mm, l (1 / 2) For a 50cl bottle formed from a preform Y having a dimension of 72.83 mm, the stretch ratios a = 3.56, b = 3.44, and c = 12.2 are of the preform X. It turned out to be smaller.

  Similarly, it has a weight p = 12.3 g which is smaller than the weight of the preform X, but larger dimensions, i.e. l = 86.0 mm, Pp = 58.4 mm, l (1/2) = 72.8 mm. For a 50cl bottle formed from a preform Z having dimensions, the stretch ratio is also smaller than that of the preform X.

  Thus, the 50cl bottle obtained from the preform Y or preform Z has dimensions of the preform Y and the preform Z with respect to the weight of the preform Z and the weight of the preform Y. It receives a smaller shrinkage effect than a bottle obtained using a preform X having a smaller dimension (Pp, l, l (1/2)).

  A reduction in the wall 10 thickness of the preform 1 having dimensions (Pp, l, l (1/2)) larger than the dimensions of the conventional preform can compensate for the resulting weight increase.

  In addition, such a reduction in wall thickness achieves a reduction in cooling time by considering that the cooling time in the process of forming the preform decreases in proportion to the square of the wall thickness of the preform. To be able to.

  Further, the thickness e of the wall 10 of the thin-wall preform 1 may change, for example, increase along the main body of the preform 1, that is, from the neck 20 of the preform 1 to the bottom surface 11 thereof. Good (Figure 2a).

  In this case, the method of the invention consists in calculating the average thickness e along the body of the wall 10 of the thin-wall preform 1. The thickness e of the wall 10 of the preform 1 is about 2.0 mm or less, and is equal to 1.5 mm for the thin wall 10 preform 1 adapted to form a bottle having a capacity of 50 cl. It is preferable.

  In this particular case, the dimensional parameters of the thin-wall preform 1 may be, for example, equal to length l = 86.0 mm, circumference Pp = 58.4 mm, l (1/2) = 72.8 mm. Which can lead to a stretch ratio equal to a = 3.44, b = 3.44, c = 11.8, preferably for a weight of the preform 1 equal to about 12.3 g.

  Thus, further in this particular case, the aspect ratio u is equal to 57.3, ie greater than the threshold 45 imposed by the constraints for molding current preforms formed from polyesters such as PET. Has a value.

  Finally, another subject of the present invention is a thermoplastic polymer, preferably a thermoplastic polyester, most preferably terephthalate, obtained by stretch blow molding of the preform 1 according to the present invention, in particular by biaxial stretch blow molding. Bottle 2 or similar container (flask, drum, etc.) formed of polyester, the number of which is derived from acid and ethylene glycol accounting for at least 92.5%. Such bottles are particularly useful in the food industry, particularly in packaged beverages such as spring water or mineral water.

Another object of the present invention is a thin wall according to the method of the present invention, which may have the following weights depending on its volume, especially water, juice, carbonated soft drink etc. A bottle or similar container formed from a preform.
For a volume of 0.5 l: weight <15 g
For a volume of 1.0 l: weight <25 g
For a volume of 1.5 l: weight <30 g

  It goes without saying that the person skilled in the art knows how to adapt the parameters of the conventional process for forming the bottle so that the thin-walled preform 1 according to the invention can be used, Now, the process for manufacturing the bottle itself will not be described in further detail.

  Of course, the present invention is not limited to the above-described embodiments shown in the accompanying drawings. Thereby, modifications can still be made without departing from the protection scope of the invention, in particular in terms of the composition of the various elements, or by substitution of equivalent techniques.

Claims (11)

From a preform (1) formed from a thermoplastic polymer, preferably a thermoplastic polyester, most preferably a polyester comprising at least 92.5% of the simple substance derived from terephthalic acid and ethylene glycol, a bottle (2 ) And the like, and a method of forming a container having an elongated body with a neck portion,
The open end of the preform (1) has the shape and dimensions of the neck (20) of the final bottle (2), and the bottle (2) has the following dimensional parameters:
Pb: the maximum outer peripheral length of the final bottle (2);
L (1/2): side half length of the final bottle (2), ie, the length measured from its bottom surface (20 ′) to the neck (20) along its shape of the final bottle (2) In a method comprising:
On the one hand, the following dimensional parameters:
Pp: the average circumference of the neutral fiber (3) of the preform (1) measured from the bottom surface of the preform (1) to the neck (20), and the cross section of the preform (1) The length of the neutral fiber (3) at
l (1/2): side half length of the preform (1), that is, the neck from the bottom surface (11) along the shape of the preform (1) of the thin wall (10) The length measured up to (20),
l: the length of the thin wall preform (1);
e: an average thickness of the thin wall (10) of the thin wall preform (1) from the bottom surface (11) to the neck (20);
u: aspect ratio, u = l / e, on the other hand, with respect to the final bottle (2), the stretch ratios a, b, c (a = Pb / Pp, b = L (1/2) / l (1/2) essentially comprising a step of stretching and blow molding a preform (1) of thin wall (10) having c = a × b),
The dimensional parameter is the following threshold condition:
e <2 mm and u> 45
Set to meet
In the stretching and blow molding steps, the stretching ratio is as follows:
a <5; b <4 and c <16
Characterized in that it is carried out to satisfy The preform (1) of the thin wall (10) is
Injecting a hot plastic melt of polymer into a mold that is not completely closed;
Closing the mold;
Pressing the melt into its final shape;
Method according to claim 1, characterized in that it is manufactured by a process consisting essentially of the step of drawing the preform (1) of the thin wall (10) from the mold. The thin wall (10) preform (1) is
Placing the molding polymer in an open mold;
Closing the mold;
Pressing the polymer melt into its final shape;
Method according to claim 1, characterized in that it is manufactured by a process comprising the step of drawing the preform (1) of the thin wall (10) from the mold. The preform (1) of the thin wall (10) is produced by using an intrinsic viscosity (IV) which indicates the viscosity at zero concentration of the polymer solution, this value being obtained on June 15, 1986 In connection with 0.5 g polymer solution in which the polymer is dissolved at 25 ° C. in 100 ml solvent mixed with orthodichlorobenzene and phenol (50/50 by weight) according to the attached standard ISO 1628/5 Calculated by determining the viscosity index (VI) in units of measured dl / g;
The method according to claim 1, characterized in that the intrinsic viscosity (IV) is 0.7 dl / g or less.   A polymer having an intrinsic viscosity (IV) of preferably 0.45 dl / g to 0.65 dl / g, most preferably 0.5 dl / g to 0.6 dl / g is selected. 4. The method according to 4. For the production of a bottle (2) having a capacity of 50 cl, the dimensional parameters of the preform (1) of the thin wall (10) are:
l = 86.0mm
Pp = 58.4 mm,
l (1/2) = 72.8 mm
The method according to claim 1, wherein the method is set to be.   A thermoplastic polymer, preferably a thermoplastic polyester, most preferably derived from terephthalic acid and ethylene glycol, used in the method according to any one of claims 1 to 6, wherein the number of simple substances is at least 92.5. A preform (1) with a thin wall (10), which is formed from polyester occupying%.   A thermoplastic polymer, preferably a thermoplastic polyester, most preferably terephthalic acid, obtained by a stretch blow molding process from the thin wall (10) preform (1) according to any one of claims 1-6. And a bottle (2) or similar container formed from polyester, the number of which is derived from ethylene glycol accounting for at least 92.5%.   9. Bottle (2) or similar container according to claim 8, having a weight of less than 15 g for a volume equal to 0.5 l.   9. A bottle (2) or similar container according to claim 8, having a weight of less than 25 g for a volume equal to 1.0 l.   9. Bottle (2) or similar container according to claim 8, having a weight of less than 30 g for a volume equal to 1.5 l.

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